I. Field of the Invention
The present invention relates to a container for medical use and, more particularly, to a container for medical use suitable for use in a closed medical system.
II. Description of the Prior Art
A closed medical system has been recently used in medical treatments such as blood donation, blood transfusion, or fluid therapy so as to prevent contact of a liquid handled (e.g., blood or a liquid medicine) with the outer environment. A container for medical use to be used in such a system must be able to transfer the liquid by means of gravity and the flexibility of the container material. The container is therefore generally made of a soft plastic. In order to keep the liquid sterile, the container for medical use of this type must be subjected to high-pressure steam sterilization and must therefore have heat resistance to withstand the high temperature of the steam. A container for medical use is frequently used to hold blood in a frozen state (at -80.degree. C.) for storage. Therefore, the container must also be resistant to low temperatures especially below freezing temperatures.
Plastics with good flexibility include soft polyvinyl chloride, ethylene-vinyl acetate copolymers, or the like. However, in view of the necessity of high-pressure steam sterilization, soft polyvinyl chloride is superior to the ethylene-vinyl acetate copolymers which are unable to withstand the high temperature of the steam.
However, soft polyvinyl chloride is inferior in resistance to low temperatures compared to ethylene-vinyl acetate copolymers and also contains a large amount of a plasticizer.
Thus, conventional containers for medical use do not simultaneously meet the requirements of resistance to high and low temperatures and involve the problem of elution of additives such as plasticizer. Therefore, it has been strongly desired that there be provided a container for medical use which has both resistance to high and low temperatures and which is also safe to use in medical applications.